Cell Review

Cells

The Cell Theory• All living things are made of one or more

CELLS.• Cells are the basic unit of structure and

function in an organism. • New cells are produced from existing cells.

2 types of cells

• Prokaryotes– Cells without a nucleus

or organelles surrounded by membranes

• Eukaryotes – Cells with a nucleus and

organelles surrounded by membranes.

Prokaryotes

• Single celled organism• Has DNA that is circular floating all around in

the cytoplasm• Only has ribosomes and no other membrane

bound organelles• Most common = bacteria

– Some can make their own food, most get food from other sources

Eukaryotes• There can be singled celled eukaryotes as well

as multicellular • Highly organized • More complex than prokaryotes

Cell membrane (plasma membrane)

• Made mainly of phospholipids (2 layers) and proteins

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

Cell membranemade of:

• Phospholipids have hydrophobic tails made of lipids and hydrophilic heads.

3 kinds of proteins-• channel-provides a path

for materials to move in and out

• marker- used for recognition

• receptor- receive signals

Cell membrane

• Acts as a boundary• Controls what enters and leaves cell• Fluid (fluid mosaic model)

– Molecules in cell membranes are constantly moving and changing (ex. cholesterol and carbohydrates)

Nucleus

• LARGEST organelle in animal cells• Surrounded by nuclear envelope• Contains nuclear pores = openings that allow

molecules to move in and out of nucleus• Contains genetic material (DNA)• Control center of the cell

Nucleolus

• Dark spot in nucleus• Assembles RNA and also ribosomes

Cytoskeleton

• Helps cell maintain shape• Help move organelles around• Made of proteins

– Microfilaments– Microtubules

Centrioles

• Made of microtubules• Only seen in animal cells during cell division• Function: Guide chromosomes during PMAT

Mitochondria

• “Powerplant of cell”• Site of cellular respiration• Burns glucose to release energy• Stores energy as ATP • Surrounded by double membrane

– Inner membrane = cristae

Ribosomes

• Can be free in cytoplasm or attached to rough ER

• Made of rRNA• Function: assembles proteins • Called the site of protein synthesis

Endoplasmic reticulum (internal network of membranes)

• Rough ER– Attached ribosomes

make proteins which are modified and transported to Golgi for export

• Smooth ER– Makes membrane lipids

(steroids)– Regulates calcium in

muscles– Breaks down toxins in

liver

Golgi Apparatus

• Looks like a “stack of pancakes” • Made of membranes• Modify, sort, and package substances from ER

for storage or export out of cell

Lysosomes

• Sac containing digestive enzymes

• Digests food molecules and unwanted cells/cell parts

• Plays a role in apoptosis “programed cell death”– Cell suicide for the good

of the organism

Movement

• Pseudopodia = “false feet” help amoebas with movement and eating (phagocytosis)

• Cilia = many and short microtubules (little hairs)

– Move cells– Move substances past cells

• Flagella = few and long microtubules (like a tail)

– Move cells

What’s special about plant cells?

• Cell wall• HUGE central vacuole• Chloroplasts• No centrioles!!

Cell wall

• Found outside the cell membrane• Provides support and protection• Made of Cellulose (carbohydrate) makes plant

sturdy• Bacteria have cell walls made of peptidoglycan

instead• Cell walls of fungi are made of chitin

Vacuoles

• Storage space for: proteins, carbohydrates, water, waste

• Contractile vacuoles control excess water in a paramecium (homeostasis)

• Huge in plant cells, small animal cells, not in bacteria

Chloroplast

• Surrounded by double membrane• Thylakoids = membrane sacs inside• Contains chlorophyll where photosynthesis

happens• Found photosynthetic cells (plants, some bacteria and protozoans)

Molecule Movement and Cells

• Passive Transport = does not require energy by the cell

• Active transport = requires energy!

Passive transport

• No energy required• Move due to gradient

– Differences in concentration, pressure, charge• Move to equalize gradient (equilibrium)

– High concentration moves toward low concentration

• 3 Types– Diffusion, osmosis, facilitated diffusion

Diffusion

• Molecules move to equalize concentration

Osmosis

• Special form of diffusion• Fluid flows from lower solute concentration• Always involves movement of water

– Into cell– Out of cell

Hypotonic = solutes in cell more than outside, fluid will flow into cell

Isotonic = solutes equal inside and out of cell

Hypertonic = solutes greater outside cell, fluid will flow out of cell

Facilitated Diffusion

• Channels (are specific) help molecule or ions enter or leave the cell

• Channels usually are transport proteins

Active transport

• Molecular movement• Requires energy (against gradient)• Example: sodium-potassium pump

Endocytosis

• Phagocytosis – cell eating

• Pinocytosis – cell drinking

Exocytosis

• Reverse of endocytosis• Cell discharge material

Cellular reproduction

• 5 ways– 1. Fission– 2. Budding– 3. Vegetative propagation– 4. Mitosis– 5. Meiosis

Binary Fission

• Prokaryotes (bacteria)• Asexual reproduction• Cell makes copy of DNA and grows in size• Membrane will divide and two new cells

formed

Budding

• Asexual reproduction• Hydra bud to form new hydra• Yeast cells undergo budding

Vegetative propagation

• Asexual reproduction in plants• Runners will grow off from the parent plant

and root to form a new identical plant.